Nickel exposure induces persistent mesenchymal phenotype in human lung epithelial cells through epigenetic activation of ZEB1

ABSTRACT: Purpose: Environmentally induced diseases, including cancer typically develop long after the exposure has occurred. However, most of the toxicological studies are conducted during active exposure. Therefore, environmental exposure-induced adverse effects that persist after cessation of exposure is poorly understood. Methods: Immortalized human bronchial epithelial cells (BEAS-2B) were cultured in Dulbecco’s Modified Eagle’s Medium (DMEM, Cellgro) supplemented with 1% Penicillin Streptomycin and 10% Fetal Bovine Serum (FBS, Atlanta Biologicals) at 37 degree C and 5 % CO2. For Ni exposure, various concentrations of NiCl2 (Sigma N6136) was added to the media and the cells were cultured for 6 weeks. Following exposure, the cells were washed and cultured in Ni-free medium for 2 weeks to obtain the Ni-washed-out cells. To obtain homogenous populations of Ni-exposed cells, the cells exposed to 100 mM NiCl2 for 6 weeks were plated in 15 cm plates in Ni-free medium at the rate of 1000, 500, 100 and 50 cells per plate. Nicely separated single colonies were picked and the populations were expanded in Ni-free medium. Results: Here we report that Ni, an environmentally prevalent, low-mutagenic carcinogen causes epithelial-mesenchymal transition (EMT) that persists even after the exposure has ceased. Ni-induced persistent EMT induction is dependent on the upregulation of ZEB1, an EMT master regulator. We found that Ni exposure resolved the bivalent chromatin environment of ZEB1 gene, thereby keeping it in a permanent ‘on’ state. The continuously expressing ZEB1 downregulated its negative regulators, thus establishing a self-sustaining positive regulatory loop. Given the importance of EMT in a number of diseases including asthma, pulmonary fibrosis, development of premalignancy, carcinogenesis and metastasis, we believe that persistent EMT induction through epigenetic activation of ZEB1 is a major step in Ni-induced human diseases.

ORGANISM(S): Homo sapiens

PROVIDER: GSE95180 | GEO | 2018/03/17

REPOSITORIES: GEO